The invention relates to a fluid conduit which comprises at least one inner conduit, which is surrounded by a leaktight, burst-proof jacket and can be subjected to internal pressure.
DE 37 39 937 A1 describes a pressure conduit for fuel comprising a pressure pipe, a jacket pipe surrounding the latter with a narrow clearance and leakage-fuel passages extending in the longitudinal direction between both pipes. On its outer curved surface, the pressure pipe, which is produced in one piece from solid material, has at least one flat for the formation of leakage-fuel passages in the form of circular segments. A pressure conduit of this kind for fuel is said to be simple to produce and to have the greatest possible dimensional stability and hence durability, even in bending, so as to reduce the risk that the pressure pipe will crack.
Regulating devices are known which are operated hydraulically. Such hydraulic regulating devices can be operated at high pressures. The pressure in the feed conduits can, for example, be up to 140 bar, and the inside diameter chosen for the feed conduit can be relatively small. The high working pressure within the hydraulic conduits requires special measures at the coupling points or flange joints as regards sealing. Leaks would lead to unwanted pressure loss and to contamination of the environment. In the case of regulating devices for turbo machines, in particular industrial turbines and turbo generators, there is furthermore the risk of fire if the hydraulic fluid is a combustible fluid.
One known method of avoiding unwanted consequences of any oil leaks such as the escape of leakage oil and the risk of fires is to surround a pressure-transmitting inner conduit with a hydraulically leaktight, burst-proof jacket. One such proposal is described, for example, in DE 33 35 580 A1.
Owing to the fact that the inner conduit is provided with a jacket at a certain clearance, the required installation volume for such a conduit is increased. In addition to a pressure-transmitting feed conduit, there is also a requirement with a control or regulating device for a return conduit which forms a return for the hydraulic fluid, since the hydraulic fluid has to be recirculated. This increases the space requirement for the conduits of control and regulating devices.